Analysis of digital modulation with unequal power allocation

In digital transmission systems for speech, audio, and video signals source encoders extract parameters which are quantized and converted into a digital representation. As the individual bits of this representation exhibit different bit error sensitivities, usually channel coding with unequal error protection (UEP) is applied. However, some transmission systems do not include channel coding for several reasons. In this situation a concept called modulation with unequal power allocation (MUPA) can be applied which achieves UEP by allocating different transmission power to the modulation symbols according to the individual bit error sensitivities. The average transmitted energy per bit remains unaffected. In this contribution we present a new detailed analysis of BPSK-MUPA and 16-QAM-MUPA, and discuss the performance improvements in terms of parameter SNR compared to systems with constant symbol energy.